JP7285245B2 - Receiving device for optical wireless communication - Google Patents

Description

TECHNICAL FIELD The present invention relates to a receiving device for optical wireless communication, and more particularly to a device for adjusting the direction of a receiving optical axis.

2. Description of the Related Art Wireless optical communication is widely used in which communication is performed between a device on the transmitting side and a device on the receiving side without using a communication line such as an optical fiber. Optical wireless communication is performed between both banks of a river in an emergency, for example. Optical wireless devices are installed on both banks of a river, and light including information is transmitted from one optical wireless device to the other optical wireless device. Optical wireless communication may also take place between two buildings. Since optical wireless communication does not use communication lines, installation costs are reduced.

The following patent documents 1 and 2 describe optical wireless devices. Patent Literature 1 describes that communication is performed with a plurality of counterparts by providing a plurality of electrical-to-optical conversion units. Further, it is described that by sending out light beams from a plurality of light emitting portions to the same partner, the light intensity increases and communication over a longer distance becomes possible. Patent Literature 2 describes a technique for adjusting the direction of light to be transmitted and received (the direction of the optical axis).

Patent Literature 3 describes a technique in which encoding and reproduction by the matched filter method are used in optical data transmission. A transmission signal is time-spread using a PN code sequence, and the signal is collected at one point on the time axis by decoding on the receiving side.

JP-A-2005-286705 JP 2015-122737 A JP 2008-268619 A

Generally, in optical wireless communication, the reception direction is adjusted after the approximate transmission direction is adjusted for each of a pair of optical wireless devices. Some optical wireless devices adjust the reception direction by an adjustment mechanism that adjusts the posture of the light receiving section. In this case, the reception direction is adjusted by the user operating the adjustment mechanism while checking the received light intensity. When adjusting the reception direction in this way, unnecessary light such as sunlight may be received, making the adjustment difficult. Also, in optical wireless communication, non-visible light such as infrared light is sometimes used. In this case, it is difficult for the user to visually adjust the receiving direction.

SUMMARY OF THE INVENTION An object of the present invention is to reliably adjust the reception direction of a receiver for optical wireless communication.

The present invention comprises a receiving unit that converts received light into a received signal that reflects the amplitude of the received light, a correlator that performs a correlation operation between the received signal and a predetermined reference code, and the an optical axis adjusting device for obtaining a reception level based on the correlation signal obtained by the correlator and adjusting the direction of the reception optical axis of the receiving section according to the reception level.

Desirably, the reference code is a PN code, and the optical axis adjusting device adjusts the direction of the receiving optical axis so that the receiving level exceeds a predetermined threshold.

Preferably, the correlator is a plurality of delayers connected in cascade, and a plurality of delayers to which the received signal is input to the first-stage delayer, and a plurality of delayers provided corresponding to each of the delayers. a multiplier that multiplies the received signal output from the delay unit corresponding to itself by the code element corresponding to itself among a plurality of code elements forming the reference code and outputs the result; , and an adder for summing the output values of each of the multipliers, and each of the delayers, where K is an integer of 2 or more, is 1/K times the code time interval of the reference code. Delay the received signal.

Desirably, the optical axis adjustment device includes an attitude adjustment mechanism that adjusts the attitude of the receiving device.

Preferably, a receiving lens is provided, and the receiving section is arranged behind the lens, and the receiving section includes an optical fiber having a tip directed toward the lens and converting light guided by the optical fiber into the received signal. and a converter, and the optical axis adjusting device includes a moving mechanism for moving the tip of the optical fiber.

Desirably, the moving mechanism moves the tip of the optical fiber in a direction along the optical axis of the lens and a direction crossing the optical axis of the lens.

Desirably, the moving mechanism includes an arranging operation of arranging the tip of the optical fiber behind the lens with the tip of the optical fiber directed toward the lens, and a maximal search operation, wherein the optical fiber An operation of moving the tip of the lens in a direction along the optical axis of the lens to search for a first maximum position where the reception level is maximum, and a plane passing through the first maximum position and intersecting the optical axis of the lens moving the tip of the optical fiber within the optical fiber to search for a second maximum position where the reception level is maximum; Position the tip of the optical fiber.

Desirably, the moving mechanism performs the maximum search operation a plurality of times, and moves the optical fiber to a position based on the second maximum position searched by performing the maximum search operation a plurality of times. Place the tip of the

ADVANTAGE OF THE INVENTION According to this invention, the receiving direction of the receiver for optical wireless communication can be adjusted reliably.

1 is a diagram showing the configuration of an optical wireless communication system; FIG. FIG. 2 is a diagram showing the configuration of an optical transmitting/receiving unit; It is a figure which shows the example of a PN signal. FIG. 4 is a diagram showing the configuration of a correlator; It is a figure which shows the structure of the receiving apparatus which concerns on application embodiment. FIG. 4 is a diagram showing the focal point of a receiving lens and the optical path behind the focal point; FIG. 4 is a diagram schematically showing an example of the operation of the tip of the optical fiber in each process;

An embodiment of the present invention will be described with reference to each drawing. The same components shown in multiple drawings are denoted by the same reference numerals to simplify the description. FIG. 1 shows the configuration of an optical wireless communication system 100 according to an embodiment of the present invention. The optical wireless communication system 100 includes a first optical wireless device 10-1 and a second optical wireless device 10-2 that perform optical wireless communication. One of the first optical wireless device 10-1 and the second optical wireless device 10-2 transmits light 102 modulated by a transmission signal including data to be transmitted to the other. The light 102 may be a modulated monochromatic light, or may be an electromagnetic wave having a longer wavelength than visible light, such as infrared rays. Alternatively, the light 102 may be visible light. In the following description, the first optical wireless device 10-1 and the second optical wireless device 10-2 may be referred to as the optical wireless device 10. FIG.

In addition to the communication mode for transmitting data to be communicated, the optical wireless device 10 has a direction of an optical axis (transmitting optical axis) of the optical wireless device 10 on the transmitting side and an optical axis (receiving light) of the optical wireless device 10 on the receiving side. It operates in the optical axis adjustment mode that adjusts the direction of the axis). In the communication mode, the transmitted signal is a digital signal representing the data to be communicated. In the collimating mode, the transmitted signal can be any digital signal. For example, it may be a digital signal whose values are all 1's. The operation of the wireless optical device 10 in the optical axis adjustment mode and each configuration used for this operation will be described below.

FIG. 2 shows the configuration of the optical transmission/reception unit 12 provided in each of the first optical wireless device 10-1 and the second optical wireless device 10-2. The optical transceiver unit 12 comprises a transmitter 14 and a receiver 22 . The transmission device 14 includes a PN signal generator 16 , a transmission section 18 and a transmission lens 20 . The PN signal generator 16 outputs a PN signal indicating a PN code (Psudo Noise) to the transmitting section 18 with a pulse time waveform. The PN code is a predetermined reference code, and is stored in common between the first optical wireless device 10-1 and the second optical wireless device 10-2.

The PN signal becomes high or low in level corresponding to the code elements "1" or "0" forming the PN code. For example, a high level of the PN signal may be associated with the code element "1", and a low level of the PN signal may be associated with the code element "0". An example of a PN signal is shown in FIG. The PN code consists of n code elements a1 to an. The PN code (a1, a2, a3...an) shown in FIG. , 1, 0). In the PN signal, a section on the time axis corresponding to the PN code (a1, a2, a3, .

Returning to FIG. 2, description will be made. A transmission signal is input to the transmission unit 18 . A transmission signal is an electrical signal containing data to be transmitted. The transmission unit 18 multiplies the transmission signal by the PN signal to generate a time-spread signal, converts the time-spread signal into light reflecting the amplitude, and transmits the light through the transmission lens 20 .

The receiving device 22 includes a receiving lens 24 , a receiving section 26 , a controller 28 and an electric platform 36 . The receiver 26 receives light through the receiving lens 24 . The receiving unit 26 converts the received light into a received signal, which is an electrical signal reflecting the amplitude of the received light, and outputs the received signal. The controller 28 comprises a correlator 30, a level determination section 32 and a control section 34. FIG. The controller 28 may be configured by a processor that configures the correlator 30, the level determination section 32, and the control section 34 by executing a program. Correlator 30 performs a correlation operation on the received signal and the PN code to generate a correlation signal, and outputs the correlation signal to level determining section 32 . The level determination section 32 obtains a reception level indicating the magnitude of the received signal based on the correlation signal, and outputs the reception level to the control section 34 .

The control unit 34 controls the electric platform 36 based on the reception level. The electric camera platform 36 may include an attitude adjustment mechanism that changes the attitude of the housing that houses the wireless optical device 10 or the housing that houses the optical transmitting/receiving unit 12 under the control of the control section 34 . The electric platform 36 adjusts the attitude of the optical transmission/reception unit 12 under the control of the controller 34 . That is, the control unit 34 causes the motorized camera platform 36 to adjust the attitude (elevation angle and azimuth of the reception optical axis) of the optical transceiver unit 12 so that the reception level exceeds a predetermined first threshold. Adjust the direction of

As will be described later, the receiving section 26 may include a fine adjustment mechanism for finely adjusting the direction of the receiving optical axis when receiving light. In this case, the control unit 34 controls the fine adjustment mechanism included in the reception unit 26 so that the reception level exceeds the predetermined second threshold.

In this way, the receiving device 22 obtains the reception level based on the correlation signal obtained by the correlator 30, and functions as an optical axis adjustment device for adjusting the direction of the reception optical axis of the receiving section 26 according to the reception level. A determination unit 32 , a control unit 34 and an electric platform 36 are provided. Moreover, in application embodiments described later, the optical axis adjustment device further includes a fine adjustment mechanism.

FIG. 4 shows the configuration of the correlator 30. As shown in FIG. The correlator 30 includes 2n delay devices Dα1, Dβ1, Dα2, Dβ2, Dα3, Dβ3, . , Mβ2, Mα3, Mβ3, . . . Mαn, Mβn. That is, multipliers Mαj and Mβj are provided corresponding to delayers Dαj and Dβj, respectively. However, j is any integer from 1 to n.

Each delay device delays the input signal by T/2 and outputs the signal. Here, T is the code time interval and corresponds to the pulse time interval of the PN signal. The delay devices Dβn, Dαn, Dβn-1, Dαn-1, . /2 and output to the next-stage delay unit. The received signal output from the receiving section 26 is input to the delay device Dβn of the first stage, and the subsequent 2n-1 delay devices sequentially delay the received signal by T/2.

Multiplier Mαj outputs a value obtained by multiplying the received signal output from delay device Dαj by code element aj. Multiplier Mβj outputs a value obtained by multiplying the received signal output from delay device Dβj by code element aj. The correlator 30 comprises a summing unit S in addition to each delayer and each multiplier. The adder/summer S outputs a correlation signal obtained by summing the values output from the multipliers Mα1, Mβ1, Mα2, Mβ2, Mα3, Mβ3, . . . Mαn, Mβn.

The correlation signal reaches a maximum value each time one PN code period PNT=nT elapses. The level determining unit 32 in FIG. 2 obtains, for example, an average value (moving average value) of a plurality of maximum values obtained in the past for a predetermined period of time as the reception level. The level determination unit 32 may obtain statistical values such as the median, maximum, minimum, and deviation values of a plurality of maximum values obtained in the past for a predetermined period of time as the reception level.

In the correlator 30 according to the present embodiment, each of a plurality of cascaded delayers delays the received signal by T/2, the received signal output from each delayer is multiplied by a code element, and each multiplication result is are summed to obtain a correlation signal. By setting the delay time in each delay device to half the code time interval T, T/2, the correlation signal reliably has a maximum value. That is, when the delay time in each delay unit is set to the code time interval T, the magnitude of the maximum value of the correlation signal may be insufficient, or the maximum value may not appear in the correlation signal. This is because the timing at which the received signal is input to each delay unit may coincide with the timing at which the code element multiplied by the received signal changes (code change timing). According to the correlator 30 according to the present embodiment, it is avoided that the timing at which the received signal is input to the delay device and the sign change timing of the received signal coincide with each other in all the delay devices. This ensures that the correlation signal has a maximum value.

Also, the correlation signal is obtained by integrating the signal time-spread by the PN code in the optical wireless device 10 on the transmission side for each PN code period of the PN signal. Therefore, even if the light received by the receiving device 22 contains noise light, a correlation signal having a sufficient signal-to-noise ratio is generated, facilitating adjustment of the direction of the receiving optical axis.

Above, a correlator 30 was shown in which each delay delays the received signal by half the symbol time interval T, T/2. Each delay may delay the received signal by 1/K of the symbol time interval T. FIG. However, K is an integer of 2 or more. The correlator 30 is provided with K·n delay devices connected in cascade, and a multiplier is provided corresponding to each delay device. Each multiplier multiplies the received signal output from the corresponding delay unit by its corresponding code element among the plurality of code elements forming the PN code, and outputs the result. The correlator 30 is provided with an adder for summing the output values of the multipliers. Common code elements are associated with groups partitioned from the top so as to include K multipliers. That is, the code element an is associated with the top group, and each of the K multipliers belonging to this group multiplies the received signal by the code element an. Code element an-1 is associated with the second group from the top, and each of the K multipliers belonging to this group multiplies the received signal by code element an-1. . . . Code element a1 is associated with the final stage group, and each of the K multipliers belonging to this group multiplies the received signal by code element a1.

Next, application embodiments of the present invention will be described. FIG. 5 shows the configuration of the receiver 22 according to the application embodiment together with the detailed configuration of the receiver 26 . The receiver 26 includes an optical fiber 40, a converter 42 and a moving mechanism 38 (fine adjustment mechanism). The receiving device 22 has a function of guiding the light incident from the receiving lens 24 to the optical fiber 40 and converting the received light into a reception signal which is an electrical signal, and also has a function of adjusting the direction of the receiving optical axis. there is In the following description, the direction from the receiving lens 24 to the outside (the left direction in FIG. 5) is defined as the front direction of the receiving device 22 . Also, the up-down direction in FIG. 5 is the up-down direction of the receiving device 22 .

An optical fiber 40 is arranged behind the receiving lens 24 with its tip directed toward the receiving lens 24 side. The optical fiber 40 extends rearward from its tip and reaches a converter 42 arranged at the rear of the receiving section 26 . The converter 42 acquires the light transmitted by the optical fiber 40, converts the light into a received signal reflecting the amplitude of the light, and outputs the received signal. The optical fiber 40 is flexible, and the tip portion is movable while the rear end connected to the converter 42 and the vicinity of the rear end are fixed. Here, the tip portion refers to the tip portion of the optical fiber 40 as well as the portion near the tip that is held by the moving mechanism 38 and moved by the moving mechanism 38 .

Correlator 30 generates a correlation signal by performing a correlation operation on the received signal output from converter 42 and the PN code, and outputs the correlation signal to level determining section 32 . As described above, the level determination section 32 obtains the reception level based on the correlation signal and outputs the reception level to the control section 34 . The control unit 34 controls the moving mechanism 38 based on the reception level.

The moving mechanism 38 moves the tip of the optical fiber 40 under the control of the controller 34 . That is, the moving mechanism 38 moves the tip of the optical fiber 40 in the front-rear direction and in a plane perpendicular to the front-rear direction while the tip of the optical fiber 40 is directed toward the receiving lens 24 .

FIG. 6 shows a focal point 54 and an optical path behind the focal point 54 when light enters the receiving lens 24 from the direction indicated by the dashed line 52 . When light is incident on the entire front surface of the receiving lens 24 from the direction indicated by the dashed-dotted lines 52 into the area sandwiched between the two dashed-dotted lines 52, the area behind the focal point 54 is a hatched rear focal area. Light is distributed at 56 .

When light enters the receiving lens 24 in different directions, the focal points 54 are formed at different positions. Each focal point formed when light is incident from all directions is on the back focal plane of the receiving lens 24 . If the position of the tip of the optical fiber 40 is displaced from the focal point 54 formed with respect to certain incident light, sufficient light will not enter the optical fiber 40 . Therefore, in the receiving device 22 according to the present embodiment, fine adjustment of the direction of the receiving optical axis is performed by bringing the position of the tip of the optical fiber 40 closer to or matching the position of the focal point 54 . This fine adjustment utilizes the fact that the optical path widens behind the focal point 54 and the focus shifts behind the focal point 54 .

That is, in the adjustment of the direction of the receiving optical axis, first, the tip of the optical fiber 40 is directed toward the receiving lens 24 side, and the tip of the optical fiber 40 is placed in the rear focal region 56 . The tip of the optical fiber 40 is then brought closer or coincident with the focal point 54 so that the intensity of the light incident on the optical fiber 40 is maximized. Placing the tip of the optical fiber 40 in the post-focal region 56 first ensures that light is incident on the tip of the optical fiber 40 and facilitates placing the tip of the optical fiber 40 in an approximate position.

The initial setting operation for arranging the tip of the optical fiber 40 toward the receiving lens 24 side and arranging the tip of the receiving lens 24 in the rear focal region 56 is performed by, for example, adjusting the posture of the optical transmission/reception unit 12 using the electric platform 36. It may be done by The control unit 34 causes the electric camera platform 36 to adjust the attitude of the optical transmission/reception unit 12 so that the reception level output from the level determination unit 32 exceeds the first threshold.

After the initial setting operation is performed, the receiving device 22 performs the following fine adjustment operation. That is, while moving the tip of the optical fiber 40 by the moving mechanism 38, the position of the tip of the optical fiber 40 that maximizes the reception level is searched for, and the tip of the optical fiber 40 is moved to that position by the moving mechanism 38. placed at the maximum position.

The fine adjustment operation will be specifically described with reference to FIG. The control unit 34 controls the moving mechanism 38 to execute the maximal search operation including the following processes (i) and (ii).

(i) The control unit 34 controls the moving mechanism 38 to move the tip of the optical fiber 40 in a direction parallel to the optical axis 50 of the receiving lens 24, thereby setting the first maximum position where the reception level is maximum. Search and locate the tip of the optical fiber 40 at the first maximum position.
(ii) The controller 34 controls the moving mechanism 38 to move the tip of the optical fiber 40 within a search plane that passes through the first maximum position and intersects perpendicularly with the optical axis 50 of the receiving lens 24. , search for the second maximum position where the reception level is maximum, and arrange the tip of the optical fiber 40 at the second maximum position.

A method of moving the tip of the optical fiber 40 within the search plane in process (ii) includes a cross scan method. In the cross-scanning method, a lateral scan is performed by moving the tip of the optical fiber 40 in the lateral direction, and the position at which the reception level becomes maximum is obtained in the lateral scan. Then, at the position where the reception level is maximized in the horizontal scan, a vertical scan is performed by moving the tip of the optical fiber 40 in the vertical direction. It is sought as the local maximum position. In cross-scanning, scanning in a first direction other than the horizontal direction may be performed, and then scanning in a second direction perpendicular to the first direction may be performed.

In the fine adjustment operation, processes (i) and (ii) are repeated until the received level when the tip of the optical fiber 40 is at the second maximum position exceeds the predetermined second threshold. If the reception level for the second maximum position exceeds the second threshold value after only performing processes (i) and (ii) once, it is not necessary to repeat processes (i) and (ii) multiple times. After the reception level when the tip of the optical fiber 40 is at the second maximum position exceeds the second threshold value, the tip of the optical fiber 40 is placed at the second maximum position so that the tip of the optical fiber 40 The part is brought closer or aligned with the focus 54 of the receiving lens 24 . As a result, the transmitting optical axis of one of the first optical wireless device 10-1 and the second optical wireless device 10-2 is aligned with the receiving optical axis of the other.

As described above, the moving mechanism 38 according to the present embodiment performs the following placement operation and maximum search operation under the control of the control unit 34 . The placement operation is the operation of placing the tip of the optical fiber 40 in the post-focal region 56 behind the receiving lens 24 with the tip of the optical fiber 40 directed toward the receiving lens 24 . This operation may be performed by the control unit 34 controlling the electric platform 36 .

The maximal search operation is an operation corresponding to processes (i) and (ii), in which the tip of the optical fiber 40 is moved in the direction along the optical axis 50 of the receiving lens 24, and the light incident on the optical fiber 40 is includes an operation of searching for a first maximum position where the intensity of is maximum. In the maximum search operation, the tip of the optical fiber 40 is moved within a plane that passes through the first maximum position and intersects the optical axis 50 of the receiving lens 24, so that the intensity of the light incident on the optical fiber 40 becomes maximum. It includes the operation of searching for the second local maximum position. The tip of the optical fiber 40 may be placed at a position based on the second maximum position. The moving mechanism 38 executes the maximum search operation a plurality of times under the control of the control unit 34, and moves the optical fiber to a position based on the second maximum position searched by executing the maximum search operation a plurality of times. 40 tips may be placed.

According to this embodiment, the tip of the optical fiber 40 is first placed in the post-focal region 56 . This ensures that the light is incident on the tip of the optical fiber 40, and facilitates the placement of the tip of the optical fiber 40 at an approximate position. Further, according to the present embodiment, the maximal search operation is performed after the tip of the optical fiber 40 is placed in the back focal region 56 . Therefore, after the transmission optical axis of the first optical wireless device 10-1 and the reception optical axis of the second optical wireless device 10-2 are first aligned, the transmission optical axis of the second optical wireless device 10-2 and the second optical wireless device are aligned. Even if the receiving optical axis of the first optical wireless device 10-1 is aligned, the transmitting optical axis of the first optical wireless device 10-1 and the receiving optical axis of the second optical wireless device 10-2, which were previously aligned, little impact on

FIG. 7 schematically shows an example of the operation of the tip of the optical fiber 40 in processes (i) and (ii). Arrow 60 indicates that the tip of optical fiber 40 has been moved from initial position A to position B by the first process (i). An arrow 62 indicates that the tip of the optical fiber 40 has been moved from position B to position C by the first process (ii). Arrow 64 indicates that the tip of optical fiber 40 has moved from position C to position D by the second process (i). Arrow 66 indicates that the tip of optical fiber 40 has moved from position D to position E by the second process (ii). Arrow 68 indicates that the tip of optical fiber 40 has moved from position E to position F, ie, focal point 54, by the third processes (i) and (ii).

When the tip of the optical fiber 40 is moved along the direction of the optical axis 50 of the receiving lens 24 , the reception level becomes maximum at the boundary between the back focal region 56 and the region outside the focal back region 56 . Therefore, the first maximum position searched by process (i) is located near the boundary, and by repeating processes (i) and (ii), the first and second maximum positions of the receiving lens 24 are located at Converge to focal point 54 . Therefore, by repeating processes (i) and (ii), one transmission optical axis of first optical wireless device 10-1 and second optical wireless device 10-2 and the other reception optical axis be matched.

10 optical wireless device, 10-1 first optical wireless device, 10-2 second optical wireless device, 12 optical transmission/reception unit, 14 transmission device, 16 PN signal generator, 18 transmission section, 20 transmission lens, 22 reception device , 24 receiving lens, 26 receiving unit, 28 controller, 30 correlator, 32 level determining unit, 34 control unit, 36 electric platform, 38 moving mechanism, 40 optical fiber, 42 converter, 50 optical axis of lens, 52 One-dot chain line showing the optical path of light incident on the lens, 54 focal point, 56 focal point rear region, 60, 62, 64, 66, 68 arrows showing movement of tip position of optical fiber, 100 optical wireless communication system, 102 light .

Claims (8)

a receiver that converts the received light into a received signal that reflects the amplitude of the received light;
a correlator that performs a correlation operation between the received signal and a predetermined reference code;
an optical axis adjustment device that obtains a reception level based on the correlation signal obtained by the correlator and adjusts the direction of the reception optical axis of the reception unit according to the reception level;
A receiver for optical wireless communication, comprising: The receiving device according to claim 1,
The reference code is a PN code,
The optical axis adjustment device is
A receiving apparatus, wherein the direction of the receiving optical axis is adjusted so that the receiving level exceeds a predetermined threshold. In the receiving device according to claim 1 or claim 2,
The correlator is
a plurality of delay devices connected in cascade, wherein the received signal is input to the delay device in the first stage;
A multiplier provided corresponding to each of the delay devices, wherein the received signal output from the delay device corresponding to itself corresponds to itself among a plurality of code elements forming the reference code. a multiplier that multiplies the code elements and outputs them;
an adder for summing the output values of the multipliers,
Each said delay device
A receiving apparatus, wherein K is an integer equal to or greater than 2, and delays the received signal by 1/K of the code time interval of the reference code. In the receiving device according to any one of claims 1 to 3,
The optical axis adjustment device is
A receiver comprising an attitude adjustment mechanism for adjusting the attitude of the receiver. In the receiving device according to any one of claims 1 to 4,
Equipped with a receiving lens,
The receiving unit
an optical fiber disposed behind the lens and having a tip directed toward the lens;
a converter for converting light guided by the optical fiber into the received signal;
The optical axis adjustment device is
A receiver comprising a moving mechanism for moving the tip of the optical fiber. In the receiving device according to claim 5,
The moving mechanism is
A receiver, wherein the tip of the optical fiber is moved in a direction along the optical axis of the lens and in a direction crossing the optical axis of the lens. In the receiving device according to claim 6,
The moving mechanism is
an arrangement operation of arranging the tip of the optical fiber behind the lens with the tip of the optical fiber directed toward the lens;
A maximal search operation,
an operation of moving the tip of the optical fiber in a direction along the optical axis of the lens and searching for a first maximum position where the reception level is maximum;
an operation of moving the tip portion of the optical fiber in a plane passing through the first maximum position and intersecting the optical axis of the lens to search for a second maximum position where the reception level is maximum. and run
A receiver, wherein the tip of the optical fiber is arranged at a position based on the second maximum position. In the receiving device according to claim 7,
The moving mechanism is
Performing the local maximum search operation multiple times,
A receiving apparatus, wherein the tip portion of the optical fiber is arranged at a position based on the second maximum position searched by performing the maximum search operation a plurality of times.

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